This invention relates generally to domestic protective systems and, in particular, to improvements in alarm systems which utilize existing AC power lines to conduct system signals.
In recent years, protective systems including provisions for security and fire alarms, have become extremely popular for domestic use and thus have had increasing commercial importance. Because of the vigorous competition in the field, the addition of features incorporated in current systems, improvements in quality and reliability, and in reducing the expense of installation and maintenance of current systems have all become very important.
One significant technique in reducing the expense of installation in protective systems is to utilize AC power lines, as already exist in the home, to conduct system signals. In this manner, the expense and installation of wires is completely eliminated in connecting the various monitored remote stations or alarm zones to each other and/or to a master receiver. One example of such a system utilizing AC power lines is disclosed in Wadsworth, U.S. Pat. No. 3,922,664.
Once a protective system has been designed utilizing existing AC power lines, it is further preferable to have circuitry which will provide the user with more information than has been obtainable in past systems, including identification of normal operation, identification of the location of any stations or zones in alarm, and identification of any malfunction of remote sensors with an identification of the location of the malfunctioning zone. In addition to providing this information, it is desirable to maintain a reliable system with high noise immunity and minimal potential for false alarms, and a system that can be maintained and expanded, if necessary, with minimal cost. These additional features have heretofore been unavailable in relatively low cost domestic protective products.